Spray gun with pneumatic material control



Feb. 8, 1938. E. GusTAFsso'N ET AL 2,107,732

SPRAY GUN WITH PNEUMATIC MATERIAL CONTROL Filed July 31, 1935 3 Sheets-Sheet l jhZ/QEZDKS Em: Gas

Feb. 8, 1938. E. GUSTAFSSON ET AL 2,107,732

SPRAY GUN WITH PNEUMATIC MATERIAL CONTROL Filed July 51, 1935 a Sheets-Sheet 2 E. GUSTAFSSON ET AL 2,

SPRAY GUN WITH PNEUMATIC MATERIAL CONTROL 3 Sheets-Sheet 3 Feb. 8, 1938.

Filed July 31, 1955 [72c (iastcfsson W 1 7223 #4277102,

Patented Feb. 8, 1938 umrsp STATES PATENT o -c1;

srnar GUN wrrn rnam'rrc MATERIAL CONTROL Eric Gnstafsaona ma Wahlin, cmugam, asslgnors to Binks Manufacturing Company, hicago,'lll., a corporation of Delaware Application July :1, i935, No. 34,056 V 8 Claims. (01. sea-140.1

fore been customary to employ spray guns constructed for enabling the user to vary both the 15 spraying rate, namely the time required for spray-coating a given surface area, the degree of atomization of the sprayed material, and the pattern momentarily produced bythe spray on a I needle valve directly, we have this trigger actuthe surface against which the spray is directed.

, 20 For example, with the material and the compressed air maintained at given pressures by the usual pressure regulators, the user of a conventional flat-spraying gun is free to effect the following departures from the continuous spraying Q of the material at the maximum'spraying rate corresponding to the said fluid supply pressures and with the spray pattern of the predetermined shape corresponding to an undiminished supply of air to all air ports of the air nozzle of the spray 30 gun:

v By only lightly retracting the trigger of the gun, which consecutively opens the air valve and the material valve, the user can halt this trigger at points intermediate of its full-open- 35 ing movement, thereby reducing the rate at which both material and air are emitted, so that the spraying-rate'is only a fraction of that for which the gun was constructed. (2) By varying the adiustment'of the air for 49 the usual side air ports from which the sprayflattening side air jets issue, the user can greatly *vary both the spray pattern and the uniformity of atomization o'f the projected material, thereby producing such streakiness or other variations 4:," in the resulting coating as to require additional "touch-up spraying for'increasing the coating at light spots and hand labor forrubbing down unduly thick portions of the coating.

' ,Consequentlmthe providing of the usual ad- 50 justment provisions, although admirable for en abling an experienced user to adapt a given gun to various materials, has left spray gun operators free to vary, the gun adjustments made by their supervisors, and theresulting waste of both time 55 and material has been particularly serious in establishments where operating. eiliciency d mands the maintaining of given adjustments.

Our present invention aims to avoid this shortcoming of the now conventional spray guns by providing a' gun construction which will not 5 permit the user'to operate the gun at less than a predetermined spraying rate, and by eliminating the usual spray-shape adjusting provisions so as to leave the user unable to change the spray pattern while using: a gun which is equipped with "a given set'of material and air nozzles, to which gun both material and air are supplied under pressures regulated at points out of his reach.

In general, we accomplish all of our above recited purposes by the cooperation of the following provisions: v

(a) Instead of having the usual trigger of the gun operate the material-discharge-controlling ate a separate control valve controlling the supply to a pneumatic valve" which automatically opens the material discharge outlet to its full extent when the trigger is retracted sufllciently to admit air to the gun.

(b) We construct our air valve so that air pressure behind the closed valve will prevent the user from opening it with a light pressure on the trigger, and so that air flowing in front of this valve as soon as it opens will reduce the resistance. By doing this, we insure a quick and complete opening of the air valve as soon as sufficient force has been applied to the trigger to start the opening of the valve.

(0) We provide means for venting the air in front of the said pneumatic valve as soon as the control valve closes in response to the releasing of the trigger, thereby insuring a closing of the material discharge outlet before air ceases to issue from the air nozzle.

(d) We eifect this venting through an'air vent 40 in'the chamber which houses the control valve, and provide means associated with the control valve for automatically closing the said air vent when the gun is in use, so as not to have the vent provision interfere with the normal oper- 5 atlon of the gun.

-(e) We provide air passage portions of adequate size for storing considerable air, so as to enhance the emission of air from the air ports of the air nozzle'o'f the gun before the material discharge begins and after the material discharge "has been halted, thereby avoiding any splashing the gun so that this trigger will open the air valve before it opens the control valve, thereby augmenting the time during which air issues from the gun both .before the beginning and after the end of the discharging of the material.

Illustrative of a suitable spray appliance construction for our above recited purposes.

Fig. 1 is a full sized side elevation of a spray gun embodying our invention, with the spray head shown in section. 1 Fig. 2 is a fragmentary rear elevation of the same gun. I Fig. 3 is a fragmentary side elevation, taken from the side opposite to that shown in Fig. 1.

Fig. 4 is a central, vertical andlongitudinal section through the body of the gun.

Figs. 5 and 6 are sections taken respectively along the correspondingly numbered lines in Fi 4. r

Fig. 7 is an enlargedcentral, vertical andlongitudinal section through rearward parts of the gun, showing the'positions of the pneumatically actuated needle valve and, of the air valve when the gun is not in use, so that both of these valves are closed. v

Fig. 8 is a similarly enlarged section, taken (along the line 8-8 of Fig. 5) through the control valve chamber and the chamber housing the air piston fastened to the material-controlling needle valve, taken when both of these valves are in their closed positions, I

Fig. 9 is a fragmentary transverse section taken along the line 9-9 of Fig. 8.

Fig. 10 is a horizontal section taken along the line Ill-I0 of Fig. 1, showing the idle position of the trigger with respect to the stems of the control valve and the air valve.

Fig. 11 is a section through the valve chambers and associated parts of a modified form of our spray gun, namely one in which the control valve chamber is disposed above the pneumatic valve chamber, taken when the gun is in operation.

In the embodiment of Figs. 1 to 10, the body of our spray gun includes a stock I having a longitudinal air passage 2 leading to a frontal air chamber 3 in the head 4 of the body. From this chamber the air issues partly alongside and aroundthe tip of a material nozzle M, and partly (past an air equalizing baille B) through the usual side air ports 5 in the opposed horns 6 of an air nozzle 1.

Depending from the rearward portion of the stock I of the gun body is a tail portion T having two superposed longitudinal bores, one being a lower bore 9 (Fig. 7) to which compressed air is admitted from an air supply pipe I0 supported within a gun handle H depending from the said tail portion. This lower bore 9 has a contraction affording a rearwardly facing seat II for an air valve I2 which has a stem I3 extending forwardly through a stufllng box I4, this air valve being continually urged forwardly toward its closure position by a compression spring I5 interposed between the said valve and a head I6 which seals the rear end of the said lower bore.

The part of the lower bore 9 forward of the valve seat II is connected by an upright port I1 to an upper longitudinal bore U, from which latter bore a port I8 leads to the air passage 2 in the gun barrel I. Rigidly mounted in the forward part of the upper bore U is a horizontal spool-like stem guide I9, the forward portion of which forms'the body of a stufling box, the part of this stem -guide between the said ports I! and I 9 being of smaller diameter than the corresponda,'1o7,7s2

ing part of the upper bore U to permit air to flow freely past it from the port II to the port l6. As

here shown, the stufiing box also includes an axiing Pis a needle valve N which closes the outlet of the material nozzle M (as in Fig. 1) when the gun is not in use. Threaded upon this needle valve, and latched against unscrewing by a locknut 2I is a piston comprising a head 22 carrying an elastic piston ring 23 which fits the said upper bore U. This piston is continuously urged forward by a compression spring 43 interposed between the piston head 22 and the head 24h of a cap 24 which effectively seals the rear end of the upper bore, except for a relatively small vent bore 25 in the said cap head 2412 which maintains atmos'pheric pressure behind the piston.

In addition to the superposed longitudinal bores 9 and U the'tail T of the gun body also includes a third longitudinal bore 26 which desirably has its axis at one side of the alined'upright ports I1 and I9 (as shown in Figs. 5, 6 and 9) and which houses the control valve C of our gun as shown in Fig. 8. This third bore 26 has a contracted bore portion affording a rearwardly facing annular seat 21 (Figs. 8 and 11) for engaging the forward end of the tubular body C of a control valve, this valve body having the forward end of its bore 26a closed by a control valve stem 28 which extends slidably through a stufling box (including a cap 29) toward the usual trigger 3i! of the spray gun. I v

The control'valve body C has its forward pore tion of a polygonal section, as shown in Fig. 9, so as to engage the bore 26 of the said third bore (which, together with a cap 3I at its rear end forms the control valve chamber of our spray un) only at circumferentially spaced portions while permitting air to flow along intermediate portions of the periphery of this valve body for the hereafter recited purpose.

The rearward portion C of the control valve body C is diametrically contracted to permit a compression spring 32 to surround it, this spring being interposed between the said cap 3| and the rearwardly facing annular portion of the larger diametered valve body part for continuously urging the control valve body toward the said seat 21. 1

being of such a length that its rear end will befreely spaced by a quite short distance from a vent or bleeder outlet 31 in the cap 3| when the control valve body is engaging the valve seat 21 as shown in Fig. 8, in which figure the said spacing has been enlarged to clarify the drawings.

The valve stem I3of the air valve and the stem 28 of the control valve both extend sufficiently forward so as to be near rearwardly facing portions of the usual trigger 3fl'which is pivoted upon a horizontal screw 38 extending through the stock I, as shown-in Figs. 1 and 7. These Fig. 10, with the trigger spaced farther from the stem I! when the gun is not in use, so that the retraction of the trigger will open the air valve before the control valve begins to open.

' To complete the air passageways, the gun body has a port lll leading, from a part of the air valve bore 9 opposite the shank portion. of the stationary spool-shaped stem guide I9 'in that bore, to a portion 28a of the control valve bore whichis forward of the valve seat 21 and of the forward end of the control valve bodyC.

The gun body also has a second port ll extending from a more rearward portion of the said control valve bore 26 to a space 42 within the lower bore U which is behind the stem. guide I! and in front of the head 22 and the piston ring 23 of the air valve, the area of each of the ports l and II being a quite small fraction of that of the upright port I'I.

With our spray gun thus constructed, the operation, which can conveniently be traced in Fig. 11, is as follows: When compressed air is supplied to the air duct II, and liquid material to theusual material inlet 44 of the gun, while the trigger depends freely, the three movable valve members are positioned as in Figs. 7, 8 and 10. The compressed air then acts solely and forwardly on the said valve l2 to assist the spring I i in holding that member in its closure position, while the air in all other portions of the gun, excepting the part of the air valve chamher 9 behind the air valve and in the air supply duct l0, is at atmospheric pressure. Consequently, an opening of the air valve requires an adequate digital pressure for overcoming both the pressure of the spring l5 and the air pressure hehind the air valve l2. However, as soon as this air valve begins to open, compressed air flows in front of the said valve head to balance the forward pressure of air behind that head, so that the resistance to the digital movement of the trigger decreases speedily. Owing to these provisions, and particularly when the air valve I2 is of a relatively large diameter (as shown in Fig. 7), the digital pressure on the trigger required for starting the opening of the air valve is such that this pressure instantly moves the air valve head l2 to the full open position shown in Fig. 11,

. instead of permitting the trigger to be halted in some intermediate position.

As soon as the trigger has been retracted to open the air valve and to slide the control valve rearwardly, the major part of the admitted compressed air flows successively through the upright ports I! and I8 and the air passage 2 to the airports of the air nozzle, so that air issues almost instantly both around the tip of the material nozzle and through the side ports 5 of the I airnozzle. A much smaller part of the admitted airalso passes through the small-diametered port 40 to the portion 26a of the control valve chamber which is in front of the control valve body C, which valve body has been moved from its idle position of Fig. 8 to its operative position of Fig. 11, thereby permitting air to flow along the arrow lines 50 to the space 42 between the rear end of'the stationary spindle guide It and the head of the piston 23 fastened to the needle valve N, so that the rearward pressure onthis piston opens the material valve by sliding the piston to the position shown in Fig. 11.

To reach the said space 42 in front of the needle-valve-actuatlng piston, the air not only must pass through the small-diametered ports 40 and M but also must flow through narrow passageway ll (Fig. 9) alongside the forward portion of the body C of the control valve. This restricted control valve stemf28 farther from the idle trigger'than that of the air valve stem l3. Consequently, .air always issues from the air nozzle of our gun considerably earlier than the material begins to issue from the material nozzle, so that there is no splashing of unatomized material at the beginning of the spraying'operation,

During the trigger-effected retraction of the control valve the rear end of the rearwardly projecting plunger 34 carried by that member closes the vent bore,(or bleeder outlet) 31 in the rear end of the control valve chamber. This plunger preferably is of such a length that the. rear plunger end is spaced from the"vent, when the gun is not operated (as in Fig. 8) by a minor fraction of thenormal travel of the control valve member, this being permitted by the spring in the latter member which is compressed (as in Fig. 11) when the vent is closed. By using such ing variations, and also to cushion the impact of the plunger on the cap ll so as to reduce wear.

When the user releases his retracting grip on the trigger III at the close of the spraying operation, the spring l5 promptly moves the air valve l2 forwardly to its closure position. The spring 32 does the same for the control valve C, thereby drawing the vent-controlling plunger 34 away from the air vent 31. The opening of the said vent permits the compressed air within the said space 42 in front of the needle-valve actuating pneumatic piston 23 to expand through the port 4| into the control valve chamber, so that this air exhausts its pressure through the said vent, thereby permitting the spring 43 to move the said piston forward so that the needle valve N closes the material discharge outlet. Since the forward pressure of the spring 32 on the said piston also ,aids in expelling the air from the said space the material nozzle after the needle valve has closed) to carry oil. any particles of material which otherwise might solidify at the mouth of the material nozzle. 7

With our heretofore described spray gun, both the resulting spray pattern and the degree of at-- omization of the material can readily be varied (according to the material which is to be sprayed, the surface shapes to be coated, and the desired spraying speed) by a suitable selection of the air nozzle, and a suitable regulation of the pressure on the air and the materials. Such selecting and regulating'belongs to the field of the. supervisor rather than the ordinary spray gun operator. By eliminating the adjusting features heretofore provided on spray guns, and by constructing our gun'so that it can only be used at its ,i'ull rate, we also eliminate the tampering which heretofore has caused much waste of time and labor with spray guns used by men of low intelligence.

By providing three adjacent bores (9, 26 and U in Fig. 5) in the tail portion T of the gun body,

occur with a. previously proposed gun in which the pneumatic piston chamber and the venting provision are both disposed far forward of the trigger. So also, by thus disposing the just recited three provisions in the tail of the gun and close both to each other and to the air passage I! in the said tail, we allow the compressed air to reach the piston cylinder without the material reduction in its pressure which occurs when the air has to flow through many times longer passages before it can reach the piston, as in the same heretofore proposed construction.

In addition, it will be obvious from Fig. 8 that the residual air, which is in front of the piston 23 when the user-releases the trigger to halt the operation of the gun, can reach the vent port 31 through a quite short path, thereby enabling the strong spring 43 behind the piston to close the needle valve while part of the large volume of air stored in the stock passage 2 and the passageways .leading thereto is still issuing from the air ports of the air nozzle of the gun. Consequently, we avoid a continued ejecting of material from the gun such as would occur with the same heretofore proposed gun construction owing to the long and repeatedly elbowed passages through which the residual air must flow before it can reach the air vent.

However, while we have heretofore described our invention as embodied in a hand-held spray appliance and as including numerous desirable features of construction and arrangement, it will be obvious that many changes might be made in all of these respects without departing either from the spirit of our invention or from the appended claims.

We claim as our invention:

1. A spray appliance comprising a body member having a material passage and an air passage presenting adjacent forwardly open outlets; a needle valve controlling the discharge of material from the material passage and movable rearwardly for permitting such discharge; the body I member also having a piston chamber behind and in axial alinement with the needle valve, and having a branch air-passage leading from the air passageway to the forwardportion of the piston chamber; a piston slidable in the said chamber and fast on the needle valve; spring means resisting the rearward movement of the said piston; a control valve controlling the flow of air to the piston chamber through the said branch airpassage; a second spring means resisting the opening movement of 'the control valve; an air valve controlling the admission of air to the said air passageway; a third spring means resisting an opening movement of the air valve; and a manually operable member pivoted on the said body member and disposed so that movement of the manually operable member in one direction will open both the air valve and the control va ve.

2. A spray appliance as per claim 1, in which the manually operable member is disposed for opening the air valve prior to the opening of the control valve; and in which the spring means associated with the air valve are effectively so much stronger than the spring means associated with the control valve, as to prevent the operator of the said manually operable member from halting the movement of the said means in the valve opening direction, after opening the air valve, before also opening the control valve.

3. A spray appliance as per claim 1, including means for venting the said forward portion of the piston chamber when the control valve is closed, and means associated with the control valve for discontinuing the said venting when the control valve is open.

4. A spray appliance as per claim 1, in which the body member of the appliance is formed to afford a control valve chamber having a vent port; including also a vent-closure member associated with the control valve, the said closure member being disposed for opening the vent when the control valve is closed, and for closing the vent when the control valve is open. 1

5. A spray gun of the type including a body member having an air passageway and a material passageway presenting adjacent outlets, a needle valve movable rearwardly against the resistance of a spring for opening the discharge outlet of chamber; a. piston fast on the needle valve and slidable in the said chamber between positions rearward of the said port, a control valve controlling the flow of air from the air passageway through the said port; spring means continually urging the control valve toward a position in which the control valve shuts oil the said flow of air; and manually operable means movable in one direction for opening the air valve and moving the control valve to permit air to flow from A the air passageway through the said port.

6. A spray gun as per claim 5, including means responsive to the position of the control valve for venting the said forward portion of the piston chamber when the said flow of air is shut off, and

for discontinuing the said venting when the control valve is open.

7. In a spray gun, a body member including a generally horizontal stock and a tail portion depending from the rearward part of the stock, the body member having an air passage extending upwardly through the said tail portion and thereafter forwardly through the said stock; a

spray-head carried by the forward portion of the body and including a forwardly opening material discharge nozzle having its axis substantially parallel to and spaced downwardly from the said stock; the tail portion of the body member including three cylinders axially coparallel with the said barrel, namely a piston cylinder alining axially with the material discharge nozzle, an air valve cylinder, and a control cylinder having its forward portion connected to a part of the said air passage between the air valve cylinder and the said barrel; the body also having a port connecting the forward portion of the piston cylinder with a more rearward portion of the control cylinder; a piston slidably disposed in the piston cylinder; a needle valve fastened to nozzle; a control valve slidable in the control cylinder and controlling the supply of air from the said air passage to the control cylinder; an air valve slidable in the air cylinder and adapted simultaneously to shut oil the supply of air to the control cylinder and the barrel; and three springs respectively urging the air valve, the piston and the control valve forwardly; the air valve and the control valve eachv having a stem projecting forwardly beyond the said tail portion or the body: and a trigger pivoted to the said barrel and adapted when swung rearwardly, to engage both of the said valve stems so as to force both the air valve and the control valve rearwardly.

8. A spray appliance of the class in which the forward end of the body of theappliance supports an air nozzle and a material nozzle adjacent to the air nozzle, in which the said body has a main air passage and a material passage respectively leading to the air nozzle and the material nozzle I and has a piston chamber formed in a rearward portion of the body and alining axially with the material nozzle, in which a piston slidable in the piston chamber is fastened to a valve controlling the discharge from the material nozzle, and in which an air valve controlling the admission of air to vthe said main air passage is openable by rearward movement of a trigger movably supchamber to the piston chamber; and by including a control valve disposed within the control valve chamber and controlling the flow of air through the said passageway, the control valve being movable in its opening direction by rearward movement of the said trigger.

ERIC GUSTAFSSON. FRITZ WAHLIN. 

